Power supplies are used in many areas of industry to provide necessary electrical energy. Many of these power supplies take AC power from the power distribution grid and convert it into the specific voltages that are needed to operate specific equipment. The converted voltages are typically DC voltages needed to power computer systems, telecommunications or other electronic equipment. Many of the power supply systems used for larger computer or telecommunications environments require very high power density units, whereby the output power is provided by a very small packaged power supply. Many of these power supply systems employ switching devices in the power train and operate in a switching mode to achieve higher efficiencies and higher power densities.
In many cases, the physical packaging requirements of switching-mode power supplies (SMPS) are in direct conflict with an optimal circuit layout for the chosen topology. Several printed wiring boards are typically needed to mount all of the necessary power train and control circuits. The power train itself may need to be split into two or more sections, where each section may be located on a different printed wiring board. This presents many mechanical and electrical design challenges. Passing large, high frequency switching currents between these printed wiring boards can be particularly difficult, especially in DC to DC applications with lower input voltages.
In conjunction therewith, the circuit and packaging design should take into account the wiring and connector current ratings. The switching currents, in conjunction with a potentially large wiring loop area afforded by the interconnecting wiring, may generate large magnetic fields. These magnetic fields may couple with and disturb the control circuitry of the SMPS. Additionally, if these fields are not adequately contained, the unit may fail to meet radiated emission requirements. Also, the leakage inductance of the wiring loops could store sufficient inductive energy to cause excessive dissipation in the components of the power supply that may result in malfunction or even failure of the components, such as snubber networks or semiconductor components, therein.
Additionally, the mechanical interface is often predefined and a conversion from an AC powered unit to a DC powered unit or an input voltage range modification must be accommodated using as much of the existing environment and equipment as possible to contain costs. Under the constraint of maintaining or even increasing output power, increasing the magnitude of an input voltage may cause some of the component voltage ratings to be exceeded or their design margins to be reduced to an unacceptable level. Conversely, reducing the magnitude of the input voltage will typically cause the power supply currents to increase for constant output power. This may cause operating and redesign problems that are even more severe depending on the magnitude of the current increases. The increased switching currents and the fact that the current carrying capacity of the interconnects may be limited due to mechanical and packaging constraints provide design challenges that should be addressed.
Accordingly, what is needed in the art is a power supply that account for more stringent requirements such as higher switching currents and frequencies therein.